If Justine Greening really is about to be airlifted out of the Department for Transport for the curious mishap of standing by official government policy, the prospect did not seem to be ruffling her on Tuesday.

A day that started with defending, again, her opposition to a third runway for Heathrow, ended with Richard Branson throwing a spanner into the west coast franchising works.

And in between, the indefatigable transport secretary cracked on with another controversial proposition, touring the Kent countryside with railway, transport and rural campaigners – as well as the Guardian – to show how locals have learned to love high-speed rail.

In picturesque Hollingbourne, Greening's bright yellow minibus arrived in a scene of otherwise pastoral bliss. A man from high-speed one announced that the bus was on top of a rebuilt tunnel where trains pass below at 240km.

"There," said Greening contentedly, "Oak trees, a horse."

Even parish councillors, for whom the memory of planning battles and tumbling house prices still induces wide-eyed apoplexy, when collaring Greening over scotch eggs in a pub admitted that the noise was fine now. Greening believes the Chilterns, the Tory heartlands and home to the next phase of high-speed rail, will eventually become similarly reconciled.

While critics accused the Department for Transport of dragging its feet on HS2, and now aviation capacity, she makes no apologies for thoroughness: "As you've seen, it takes me longer to get to a final conclusion, but when I do I believe in it. And when I reach it, it's one I feel that I've gone into every detail to get right."

Greening's allies believe she has reason to feel her cabinet place is safe: first, moving her would so clearly signal a U-turn on Heathrow that David Cameron would be launched into a battle he doesn't wish to fight, yet.

Second, the demographics of the current cabinet would not be helped by losing a state-school educated northern woman. As Greening put it: "Hopefully I am the right kind of person to understand what things mean to local communities."

Third, Greening really seems to like the stuff that others might blanch at. She seemed rapt on Tuesday, nodding enthusiastically as veterans of HS1 gave presentations on "outcome-based commitments" in a pistachio-painted windowless backroom at Ashford station. Invited to scrutinise noise-mitigating concrete barriers from a footbridge near Ashford, she responded with genuine interest, where one might imagine say, Jeremy Hunt, opting for the sweet relief of an oncoming Eurostar.

But all carefree trips to Kent idylls must come to an end. At Ebbsfleet, as Greening slipped into the station cafe to buy a Coke, the TV news headlines switched from Heathrow expansion to the west coast mainline row sending her advisers into a spin.

She thanked the assembled rail people for coming along, then paused. And with just the faintest hint of uncertainty, added: "I'm sure I'll be back."